Category Archives: Software Defined Radio

Radio Waves: New Quantum Receiver, Virus and Distance Learning by Radio, BBC Woofferton Early Days, and Hello Morse

Radio Waves: Stories Making Waves in the World of Radio

Because I keep my ear to the waves, as well as receive many tips from others who do the same, I find myself privy to radio-related stories that might interest SWLing Post readers. To that end: Welcome to the SWLing Post’s Radio Waves, a collection of links to interesting stories making waves in the world of radio. Enjoy!

Many thanks to SWLing Post contributors Andrea, Kim Andrew Elliott, Dave Porter, and Phillip Novak for the following tips:

New quantum receiver the first to detect entire radio frequency spectrum (Phys.org)

A new quantum sensor can analyze the full spectrum of radio frequency and real-world signals, unleashing new potentials for soldier communications, spectrum awareness and electronic warfare.

Army researchers built the quantum sensor, which can sample the radio-frequency spectrum—from zero frequency up to 20 GHz—and detect AM and FM radio, Bluetooth, Wi-Fi and other communication signals.

The Rydberg sensor uses laser beams to create highly-excited Rydberg atoms directly above a microwave circuit, to boost and hone in on the portion of the spectrum being measured. The Rydberg atoms are sensitive to the circuit’s voltage, enabling the device to be used as a sensitive probe for the wide range of signals in the RF spectrum.

“All previous demonstrations of Rydberg atomic sensors have only been able to sense small and specific regions of the RF spectrum, but our sensor now operates continuously over a wide frequency range for the first time,” said Dr. Kevin Cox, a researcher at the U.S. Army Combat Capabilities Development Command, now known as DEVCOM, Army Research Laboratory. “This is a really important step toward proving that quantum sensors can provide a new, and dominant, set of capabilities for our Soldiers, who are operating in an increasingly complex electro-magnetic battlespace.”

The Rydberg spectrum analyzer has the potential to surpass fundamental limitations of traditional electronics in sensitivity, bandwidth and frequency range. Because of this, the lab’s Rydberg spectrum analyzer and other quantum sensors have the potential to unlock a new frontier of Army sensors for spectrum awareness, electronic warfare, sensing and communications—part of the Army’s modernization strategy.

“Devices that are based on quantum constituents are one of the Army’s top priorities to enable technical surprise in the competitive future battlespace,” said Army researcher Dr. David Meyer. “Quantum sensors in general, including the one demonstrated here, offer unparalleled sensitivity and accuracy to detect a wide range of mission-critical signals.”

The peer-reviewed journal Physical Review Applied published the researchers’ findings, Waveguide-coupled Rydberg spectrum analyzer from 0 to 20 GigaHerz, co-authored by Army researchers Drs. David Meyer, Paul Kunz, and Kevin Cox[…]

Virus and distance learning by radio (1937, 1946) (AE5X Blog)

Six to eight decades ago polio was one of the most feared diseases in the US. In 1952 alone, 60,000 children were infected, 3000 died and many more were paralyzed.
The most severe outbreaks were in 1937 and 1946. My father was a victim of the 1946 epidemic, suffering minor paralysis in one leg as a child.

In 1937, many schools around the country closed, as did public pools, movie theaters and parks. But the Chicago public school system took an innovative approach.

During that period, 80% of US households contained a radio. This allowed 325,000 children in grades 3-8 to continue their education at home via radio lessons aired by six Chicago radio stations (WENR, WLS, WIND, WJJD, WCFL, WGN) that donated time for the purpose.

Program schedules for each day were printed in the morning paper. Home with more than one radio & more than one child often set up radios in different rooms so that each child could hear the appropriate grade’s lesson.

This continued for one month…until schools reopened in late September of that year.

Curriculum was developed by teachers and monitored over the air by school officials. After each episode, a limited number of teachers were available for phone calls. A large number of the calls were from parents distressed that they could not clearly receive the broadcasts.[Continue reading…]

BBC Woofferton Early Days (Ludlow Heritage News) [PDF]

Very few structures are left in the Ludlow area which can be traced back to the Second World War. However, look five miles south of the town towards the rise of the hills and a tracery of masts can be seen. Go closer, and a large building can be found by the road to Orleton, surrounded now by a flock of satellite dishes, pointing upwards. The dishes are a sign of the recent past, but the large low building was made for the war-time radio station aimed at Germany.

This little history attempts to tell the story of the British Broadcasting Corporation’s transmitting station at Woofferton near Ludlow in Shropshire during the first years of its existence. When and why did the BBC appear in the Welsh border landscape with a vast array of masts and wires strung up in the air? The story begins in 1932, when the BBC Empire Service opened from the first station at Daventry in Northamptonshire. Originally, the service, to link the Empire by wireless, was intended to be transmitted on long-wave or low frequency. But, following the discovery by radio amateurs that long distance communication was possible by using high frequency or short waves, the plan was changed. Later in the decade, the BBC expanded the service by also broadcasting in foreign languages. Although Daventry had a distinguished name in the broadcasting world, it was never technically the best place for a short-wave site, being on a hill and close to a growing town.

This article can be found in the Ludlow Heritage News: click here to download the full PDF.

Hello Morse: A collection of AI and Chrome experiments inspired by Morse code on Android Gboard (Google)

Developer Tania Finlayson found her voice through Morse code. Now she’s partnering with Google to bring Morse code to Gboard, so others can try it for accessible communication.

Morse code for Gboard includes settings that allow users to customize the keyboard to their unique usage needs. It works in tandem with Android Accessibility features like Switch Access and Point Scan.

This provides access to Gboard’s AI driven predictions and suggestions, as well as an entry point to AI-powered products, like the Google Assistant.[…]

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New RX-888 MK II SDR Receiver on the Way

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Jinze (Justin) Peng, developer of the high performing, high value RX-888 SDR, has just announced an improved “MK II” version.

I’ve been very pleased with my original RX-888 in all performance aspects, and it’s wideband demodulation and IQ WAV recording have opened up new DXing possibilities (small capacity hard drives need not apply :^)

The new receiver is now appearing on eBay and AliExpress.

Details:

We are pleased to announce the second-gen of RX888. RX888 mkII is the new generation of RX888 with the following improvements and enhancements:

1. Add a tunable (variable) attenuator in the HF path, which can tune from 0 to -31.5dB.

2. Change the fixed LNA of RX888 to a VGA, which gives the -10dB to +33dB range. VGA applies to both HF and VHF.

3. Use the newer generation of tuner chip R828D instead of R820T2.

4. Use an enhanced version of 64M LPF to improve image rejection further.

5. A jumper can select the internal reference clock or an external 27Mhz reference clock.

The primary motivation is giving users smaller granularity control on the RF front-end and a big dynamic range to fit the demands of both strong and weak signals receiving. The tunable range is -41.5dB to +33dB for HF and 0db to 55dB for VHF, which covers most use cases.

During the mkII development, we are working very closely with the original author of BBRF103, IK1XPV, on his new universal driver. The new driver supports RX888 and RX888 mkII now. The new driver can download here: https://github.com/ik1xpv/ExtIO_sddc. And we expect the power of open source will significantly improve the software support and the lifetime of RX888.

Guy Atkins is a Sr. Graphic Designer for T-Mobile and lives near Seattle, Washington. He’s a regular contributor to the SWLing Post.

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Build an affordable (but stealthy) Magnet Wire Vertical Loop antenna to mitigate condo QRM

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Many thanks to SWLing Post contributor, TomL, who shares the following guest post:

Magnet Wire Vertical Loop Antenna

by TomL

For those of you in a noisy condo like me, the environment does not give me many options. I was experimenting with a YouLoop on the wooden porch with somewhat acceptable results. For its size, it is an excellent performer, especially on the lower bands. Here is a very interesting review of the YouLoop, including close-up pictures of the innards of the phase inverter and 1:1 balun, by John S. Huggins. However, it is not waterproof and I was concerned about the ice and snow ruining it. I could tape up the connectors with waterproof tape but I also wanted something with a bigger capture area. A magnet wire stealth antenna might be just the thing!

I just happened to have a waterproof 1:1 ATU balun from Balun Designs that I was going to use for future Amateur Radio use whenever I get around to passing the next level test; it is total overkill for what I intended to use it for. It would make a good connection point and (this one) also acts as an RF choke as well. One can make a 1:1 balun by buying the right Type of ferrite core and winding it yourself. Here is just one idea from Palomar Engineers.

So I dusted it off, went to a local store to get a 100 foot spool of 26 gauge magnet wire and tested it strung up around my living room. It came out to be a rectangle about 42 feet in circumference. Results were usable. I expected lots of noise and there is a great deal across the bands, so only the strongest shortwave stations were received. However, I was surprised by how strong the mediumwave band was and good to listen to without an amplifier.

I am ambivalent towards trying to perfectly match the impedance since this is a broadband receive-only antenna and the impedance will vary greatly over MW and SW bands. And I don’t want to mess with a remotely controlled tuned loop since this antenna was destined for the outdoor porch. I tried a Cross Country Wireless preselector at my desk but had some mixed results. I later found out, by disconnecting things in series, that the preselector inline raised the noise level about 5 dBm, so I took it out for now. Perhaps it needs more internal shielding or the connecting cable is bad.

Polarization is an issue, too. I have read that most man-made noise (QRM) is vertically polarized, so why would I use a vertically oriented loop? Then I saw David Casler’s video on loop antennas where he explains that connecting a vertical loop antenna at the bottom or the top makes it horizontally polarized (connecting the coax on the side makes it vertically polarized). I never knew that! Horizontal polarization will mitigate some of the offending QRM as well as match the polarization of mediumwave band transmitters. Furthermore, I read that a horizontal loop will have poor signal pickup at low frequencies because it is not high enough off the ground, similar to a horizontal dipole. For now, a vertical loop connected to facilitate horizontal polarization is what I want.

A note about wire size. People make a big deal about it but those are mostly amateur radio people. Transmission depends on efficiency so things like wire size, skin effect, standing waves, and other things matter (see here, for example). With a receive-only antenna it is OK to use very thin wire. Resonance can matter if you want the last ounce of signal strength with an antenna tuner, like in high-Q type loops where the bandwidth is very narrow and you are using a multi-turn loop with variable capacitor and a pick-up coil of wire to the receiver. Comparatively, my simple loop is depending more on a single turn of wire, the aperture size, length of wire for its performance, and carefully isolating the feedline coax using RF chokes at both ends.

Here is one example of a strong station from Cuba I was able to record because WLW was off the air for some unexpected reason.

Radio Reloj, Cuba 870 kHz (At the end, you can hear WLW come back online with CBS news):

Side note about Radio Reloj on Wikipedia, the strange format seems to fit well with a totalitarian regime, including a “corrector” who “corrects the content/writing errors to meet the requirements”. Read the wiki link for yourself. Not a society I want to live in, thank you very much!

Example of 80 meter band performance – Greetings to a new person from members of the “Awful, Awful, Ugly Net”, 3855 kHz:

Encouraged by the results, I “installed” the magnet wire around the support beams of the wooden porch, wrapping it carefully to create a square loop. Holding it in place is a brick at each bottom corner since I am not allowed to nail anything into the Association-owned porch. The length came out to about 32 feet (8 feet per side), so I trimmed it and connected to the balun. I also added an RF choke at the Airspy HF+ input from Palomar Engineers which helped bring noise down a couple of S-units. That might not sound like a lot but by also shutting off the living room air filter and an AC switch with “wall-wart” AC power adapters on it, I was able to reduce the noise a little bit more. There is still a lot of noise from the neighbors, so it is not a perfect situation.

Here are two examples of reception with the outside installation.

Gateway 160 Meter Radio Newsletter, broadcast (in AM) by WA0RCR every Saturday on 1860 kHz:

Side note about the Radio Newsletter. I stumbled on it when using the YouLoop and found that some of the content is very interesting and informative. Of course it is geared mostly towards amateur radio but some of the news items are of general radio interest as well. It airs 1pm Saturday through 2am Sunday, USA Central Time. Obviously, many segments repeat during that lengthy timeframe and reception depends on propagation from Missouri.

KDDR 1220 kHz, West Fargo, ND station ID (presumably “nighttime” power of 327 watts):

The shortwave bands are still a noisy disaster but signal levels are higher compared to the YouLoop. Only the strongest stations come in like WRMI, WHRI, Radio Espana, Radio Habana, and CRI. And I can hear the loudest amateur radio operators.

Just for grins, here is Radio Rebelde on 5025 kHz when band conditions were above average:

Another phenomenon I am looking into is the reception pattern of a vertical loop. Less than 1/10th wavelength, the null is through the center of the loop. At one wavelength, the null manifests in the plane of the wire loop. They are too close to phase them but switching between two directional loop antennas might improve reception depending on frequency. We shall see in the future.

At least for now, I have a decent mediumwave band which performs better than the useful CCrane Twin-Ferrite amplified loop antenna that was used in the (noisy) indoors, I can hear the 160 & 80 meter amateur bands better, and the reception of the strongest shortwave broadcasters are more predictable. Not bad for four dollars of wire!

Brilliant, Tom! Again, I love how you’ve not only made an inexpensive antenna, but you’ve even done it within your HOA regulations. You’re right, too: if you’re not transmitting into an antenna, it blows the experimentation door wide open! Thank you once again for sharing your project with us.

Click here to check out all of Tom’s guest posts and portable adventures!

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Is AM synchronous detection a crucial portable radio feature?

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Many thanks to SWLing Post contributor, Mike, who writes with the following question:

How important is AM Sync for a portable radio? Is it essential or a deal breaker?

That’s a great question, Mike, and one I don’t think I’ve directly addressed it here on the SWLing Post oddly enough.

Synchronous detection is actually a fairly deep topic to explore–and everyone has their own opinion–but I get the impression that you’d like a simple answer, so I’ll try to keep this as brief as possible. You might follow the comments section of this post as I’m sure some SWLing Post readers will share their thoughts on synchronous detection and how important it is for them.

So what is Synchronous Detection?

I like this concise Wikipedia answer:

In electronics, a synchronous detector is a device that recovers information from a modulated signal by mixing the signal with a replica of the un-modulated carrier. This can be locally generated at the receiver using a phase-locked loop or other techniques. Synchronous detection preserves any phase information originally present in the modulating signal. Synchronous detection is a necessary component of any analog color television receiver, where it allows recovery of the phase information that conveys hue. Synchronous detectors are also found in some shortwave radio receivers used for audio signals, where they provide better performance on signals that may be affected by fading. To recover baseband signal the synchronous detection technique is used.

How does synchronous detection help shortwave, mediumwave, and longwave listeners?

As the Wikipedia article notes above, sync detection can help “provide better performance on signals that may be affected by fading.”

In short: a solid synchronous detector can help stabilize an AM signal which then can help with overall signal intelligibility.

In some modern portable radios, at least, this could come at the expense of audio fidelity (see caveat below).

I use sync detection when the bands are rough, noisy, and QSB (fading) is affecting signals.

A good sync detector will help clean-up and stabilize the signal so that you can hear voice information with less listener fatigue. Sync detectors are also great tools for grabbing station IDs when propagation is less stable. If you have a receiver with selectable sideband synchronous detection, it can also be used as a tool for eliminating adjacent signal interference.

Caveat? Sync detectors vary in terms of quality.

The PL-880 has a synchronous detection “hidden” function. I’m sure it’s hidden because it’s so ineffective. The PL-880 is a fantastic portable, but don’t bother using the sync detector.

Many modern DSP portables sport synchronous detection, but they’re not terribly stable and the audio fidelity can take a big hit as well. Poor sync detectors can make audio sound “tinny” and narrow.

If a sync detector isn’t effective a providing a stable lock on a signal, then it’s pretty much useless. Why? If it can’t maintain a stable lock, it’ll produce very unstable shifting audio, often with the occasional heterodyne sound popping in as well. In those cases, it’s better to turn off synchronous detection.

Benchmark legacy tabletop receivers and modern Software Defined Radios (SDRs) typically have solid, effective sync detectors. Indeed, I rarely have the AM synchronous detector disengaged on my WinRadio Excalibur–that particular SDR and application enhance audio fidelity through sync detection.

I find that I use sync detection less with my Airspy HF+ Discovery and SDRplay RSPdx, for example, because the OEM applications natively does a brilliant job managing unstable signals.

In terms of portables, I’ve always considered the sync detector of the Sony ICF-2010, Sony ICF-SW7600GR, and PL-660/PL-680 to be pretty solid. I’m sure readers can suggest even more models.

Is sync detection an essential feature on a portable radio?

Not for me. But I do admit that I value the radios I own that sport a good sync detector.

For some SWLs and DXers, however? It might very well be a deal-breaker if a radio doesn’t have a sync detector, or if its sync detector doesn’t function well.

What do you think?

Is the lack of sync detection a deal-breaker for you? When do you employ sync? Please comment!

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April’s collection of Japanese language WebSDR recordings for December 2020

New SDRplay-related software installer scripts

Looking back at 2020: What radios were in heavy rotation at your home and in the field–?

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This morning, I’m looking at the calendar and I see and end in sight for 2020. I think most of us can agree that 2020 will be one for the history books, in large part due to the Covid-19 global pandemic which has had a pretty dramatic affect on many of our lives. It certainly brough my planned travels to a halt. I think many of us are quite happy to show 2020 the door!

As each year comes to a conclusion, I often look back at my radio activities during that year and see how it played out. I especially note the radios I used most heavily throughout the year.

Since I evaluate and test radios, models that are new to the market obviously get a lot of air time. Still, I’m also known to pull radios from the closet and give them some serous air time.

I’m very curious what radios you gave the most air time in 2020?

Here’s my list based on type/application:

Portable shortwave receivers

Since they’re new to the market, both the Tecsun PL-990 (above) and Belka DX (below) got a lot of air time.

I do like both radios and even took the pair on vacation recently even though packing space was very limited. I see the Belka DX getting much more air time in the future because 1.) it’s a performer (golly–just check out 13dka’s review of the Belka DSP) and 2.) it’s incredibly compact. The Belka now lives in my EDC bag, so is with me for impromptu listening and DXing sessions.

A classic solid-state portable that also got a lot of air time this year was the Panasonic RF-B65. Not only is it a performer, but it has a “cool” factor that’s hard to describe. I love it.

Tabletop portables

In a sense, the C.Crane CCradio3 got more play time than any of my radios. It sits in a corner of our living area where we tune to FM, AM and weather radio–90% of the time, though, it’s either in AUX mode playing audio piped from my SiriusXM receiver, or in Bluetooth mode playing from one of our phones, tables, or computers. In October, the prototype CCRadio Solar took over SiriusXM duty brilliantly. I’m guessing the CCRadio3 has easily logged 1,600 hours of play time this year.

Of course, the Panasonic RF-2200 is one of my all-time favorite vintage solid-state portables, so it got a significant amount of field time.

Software Defined Radios

While at home the WinRadio Excalibur still gets a large portion of my SDR time, both the AirSpy HF+ Discovery and SDRplay RSP DX dominated this space in 2020.

The HF+ Discovery was my choice receiver for portable SDR DXing and the RSPdx when I wanted make wide bandwidth recordings and venture above VHF frequencies.

Home transceivers

Without a doubt the new Mission RGO One 50 watt HF transceiver got the most air time at home and a great deal of field time as well. It’s such a pleasure to use and is a proper performer to boot!

My new-to-me Icom IC-756 Pro, however, has become my always-connected, always-ready-to-pounce home 100W HF transceiver. It now lives above my computer monitor, so within easy reach. Although it’s capable of 100+ watts out, I rarely take it above 10 watts. The 756 Pro has helped me log hundreds of POTA parks and with it, I snagged a “Clean Sweep” and both bonus stations during the annual 13 Colonies event.

Field transceivers

The new Icom IC-705 has become one of my favorite portable transceivers. Not only is it the most full-featured transceiver I’ve ever owned, but it’s also a brillant SWLing broadcast receiver. With built-in audio recording, it’s a fabulous field radio.

Still, the Elecraft KX2 remains my choice field radio for its portability, versatility and incredibly compact size. This year, in particular, I’ve had a blast pairing the KX2 with the super-portable Elecraft AX1 antenna for quick field activations. I’ve posted a few field reports on QRPer.com and also a real-time video of an impromptu POTA activation with this combo:

How about you?

What radios did use use the most this year and why? Did you purchase a new radio this year? Have you ventured into the closet, dusted off a vintage radio and put it on the air?

Please comment!

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